The present invention relates to rotary compressors assembled in refrigerating cycles of various types of refrigerating machines, refrigerators, air conditioners and the like, particularly for reducing noise and increasing a compression efficiency by improving rotary type compression mechanisms.
In general, a rotary compressor of this kind is assembled to a refrigerating cycle provided for various types of refrigerating machines, refrigerators, air conditioners and the like. In such rotary compressor, a rotary type compression mechanism to be driven by an electric motor is accommodated in a sealed casing and a refrigerant compressed by the rotary type compression mechanism is discharged from a discharge chamber into the refrigerating cycle through the sealed casing.
The rotary type compression mechanism of a conventional rotary compressor has a cylinder molded through a casting process and a refrigerant sucked from the suction port of the cylinder which is compressed in the cylinder. The refrigerant compressed in the cylinder is discharged into a main muffler chamber or a sub-muffler chamber through a discharge chamber formed to a main bearing side or a sub-bearing side. The main muffler chamber and the sub-muffler chamber are formed by a bearing cover covering the main bearing and the sub-bearing.
The refrigerant discharged into the sub-muffler chamber is introduced into the main muffler chamber through a communication hole and then introduced into the sealed chamber from the main muffler chamber.
Since the conventional rotary compressor has a discharge chamber formed on the main bearing side or the sub-bearing side, it is difficult for the discharge chamber to ensure a sufficient volume. Furthermore, since a discharge passage formed to the main bearing and the sub-bearing is arranged as the discharge chamber accommodating a discharge valve, it is difficult to define a chamber space having a substantial volume. In addition, in the conventional rotary compressor, since a cutout for a discharge port must be formed to an end surface of the inner periphery of the cylinder, it is difficult to reduce a top clearance because of the existence of the cutout, which causes a problem in the improvement of compression efficiency and reduction of noise.
On the other hand, for example, Japanese Utility Model Laid-Open Publication No. SHO 62-20186 shows a prior art providing a rotary compressor which is molded through a casting process and has a discharge chamber formed in a cylinder. In the rotary compressor of this kind, a hole is defined in the cylinder in parallel with a cylinder bore by means of a drill or the like and is used as a discharge chamber, and a discharge valve called a curl valve is accommodated in the discharge chamber, which communicates with a cylinder bore through a discharge port.
In the conventional rotary compressor of the above structure, after the cylinder is molded by casting, a discharge port formed to the inner periphery of a cylinder bore is cut by a cutting tool so as to obtain a required inner peripheral shape of the cylinder bore.
In the conventional rotary compressor having a discharge port defined in the cylinder, after the cylinder is molded by casting, a hole is drilled to the cylinder in parallel with a cylinder bore as a discharge chamber and a curl valve is accommodated therein. In this case, however, it is difficult for the discharge chamber to be formed to have a large size, and the vicinity of the discharge port must be mechanically and physically strengthened because the cylinder is made by casting. Consequently, a sufficient wall thickness must be provided between a blade groove, and the discharge port by causing the discharge port (discharge hole) to be spaced apart from the blade groove, and also a certain degree of a volume must be secured to the discharge port. Thus, a problem arises in the improvement of a compression efficiency and the reduction of noise because it is difficult to reduce a top clearance and to increase the volume of the discharge chamber formed in the cylinder.
Furthermore, in a conventional rotary compressor having a discharge chamber formed by a hole drilled in the cylinder, there is provided a further problem of forming the discharge chamber to be covered in the height direction of the cylinder. In the conventional rotary compressor having a discharge chamber formed to a main bearing and a sub-bearing and a discharge valve disposed in the discharge chamber, it is difficult to assemble the discharge valve because a sufficient volume cannot be ensured to the discharge chamber, and it is also difficult to sufficiently reduce noise resulting from the operation of the rotary compressor because a refrigerant is discharged into a sealed casing without sufficiently damping the pressure pulsation of the refrigerant.
Further, in the conventional rotary compressor, since a suction port defined to the cylinder is machined to a circular shape, the suction port has a large width of opening in the rotational direction (rolling direction) of a roller piston, thus the start of compression effected by a roller piston being delayed, and there is a possibility that a compression efficiency is reduced accordingly.